Messages in this thread | | | Subject | Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu | From | Peter Zijlstra <> | Date | Sun, 21 Nov 2010 18:44:33 +0100 |
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On Sun, 2010-11-21 at 22:04 +0800, Lin Ming wrote: > On Sun, 2010-11-21 at 20:46 +0800, Andi Kleen wrote: > > > > > > 2. Uncore pmu NMI handling > > > > > > All the 4 cores are programmed to receive uncore counter overflow > > > interrupt. The NMI handler(running on 1 of the 4 cores) handle all > > > counters enabled by all 4 cores. > > > > Really for uncore monitoring there is no need to use an NMI handler. > > You can't profile a core anyways, so you can just delay the reporting > > a little bit. It may simplify the code to not use one here > > and just use an ordinary handler. > > OK, I can use on ordinary interrupt handler here.
Does the hardware actually allow using a different interrupt source?
> > > > In general since there is already much trouble with overloaded > > NMI events avoiding new NMIs is a good idea. > > > > > > > > > + > > > +static struct node_hw_events *uncore_events[MAX_NUMNODES]; > > > > Don't declare static arrays with MAX_NUMNODES, that number can be > > very large and cause unnecessary bloat. Better use per CPU data or similar > > (e.g. with alloc_percpu) > > I really need is a per physical cpu data here, is alloc_percpu enough?
Nah, simply manually allocate bits using kmalloc_node(), that's something I still need to fix in Andi's patches as well.
> > > + /* > > > + * The hw event starts counting from this event offset, > > > + * mark it to be able to extra future deltas: > > > + */ > > > + local64_set(&hwc->prev_count, (u64)-left); > > > > Your use of local* seems dubious. That is only valid if it's really > > all on the same CPU. Is that really true? > > Good catch! That is not true. > > The interrupt handler is running on one core and the > data(hwc->prev_count) maybe on another core. > > Any idea to set this cross-core data?
IIRC you can steer the uncore interrupts (it has a mask somewhere) simply steer everything to the first cpu in the nodemask?
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